package com.puhui.lib.utils.encrypt;

import java.io.ByteArrayOutputStream;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.ObjectInputStream;
import java.io.ObjectOutputStream;
import java.security.InvalidKeyException;
import java.security.Key;
import java.security.KeyFactory;
import java.security.KeyPair;
import java.security.KeyPairGenerator;
import java.security.NoSuchAlgorithmException;
import java.security.PrivateKey;
import java.security.PublicKey;
import java.security.SecureRandom;
import java.security.Signature;
import java.security.interfaces.RSAPrivateKey;
import java.security.interfaces.RSAPublicKey;
import java.security.spec.PKCS8EncodedKeySpec;
import java.security.spec.X509EncodedKeySpec;
import java.util.HashMap;
import java.util.Map;

import javax.crypto.BadPaddingException;
import javax.crypto.Cipher;
import javax.crypto.IllegalBlockSizeException;
import javax.crypto.NoSuchPaddingException;

import Decoder.BASE64Decoder;
import Decoder.BASE64Encoder;

/**
 * Copyright: 人人普惠
 * Created by TangJian on 2017/2/14.
 * <p>
 * Description: 字符串格式的密钥在未在特殊说明情况下都为BASE64编码格式<br/>
 * 由于非对称加密速度极其缓慢，一般文件不使用它来加密而是使用对称加密，<br/>
 * 非对称加密算法可以用来对对称加密的密钥加密，这样保证密钥的安全也就保证了数据的安全
 * <p>
 * Modified: by TangJian on 2017/2/14.
 */

public class RsaEncryptUtil {

//    public static void main(String[] args) {
//        String content = "tangjian";
//
//        String result = encrypt(content);
//        System.out.println("DMLog*******  ".concat(result));
//        System.out.println("DMLog*******  ".concat(decrypt(result)));
//    }

    public static final String ALGORITHM = "RSA";
    //指定key位数
    private static int KEY_SIZE = 1024;  //max 65536
    //指定公钥存放的文件
    private static String PUBLIC_KEY_FILE = "public_key.dat";
    //指定私钥存放的文件
    private static String PRIVATE_KEY_FILE = "private_key.dat";

    private static boolean haveGeneratePair = false;

    public static void generateKeypair() {
        if (!haveGeneratePair) {
            try {
                SecureRandom secureRandom = new SecureRandom();
                //需要一个KeyPairGenerate来生成公钥私钥钥对
                KeyPairGenerator keyPairGenerator = KeyPairGenerator.getInstance(ALGORITHM);
                keyPairGenerator.initialize(KEY_SIZE, secureRandom);
                //生成
                KeyPair keyPair = keyPairGenerator.generateKeyPair();
                PublicKey publicKey = keyPair.getPublic();
                PrivateKey privateKey = keyPair.getPrivate();

                ObjectOutputStream publicOs = new ObjectOutputStream(new FileOutputStream(PUBLIC_KEY_FILE));
                ObjectOutputStream privateOs = new ObjectOutputStream(new FileOutputStream(PRIVATE_KEY_FILE));

                publicOs.writeObject(publicKey);
                privateOs.writeObject(privateKey);
                publicOs.close();
                privateOs.close();
                haveGeneratePair = true;
            } catch (NoSuchAlgorithmException | IOException e) {
                e.printStackTrace();
            }
        }
    }

    public static String encrypt(String content) {
        try {
            generateKeypair();
            //取出公钥
            ObjectInputStream publicIs = new ObjectInputStream(new FileInputStream(PUBLIC_KEY_FILE));
            Key publicKey = (Key) publicIs.readObject();
            publicIs.close();

            //开始使用
            Cipher cipher = Cipher.getInstance(ALGORITHM);
            cipher.init(Cipher.ENCRYPT_MODE, publicKey);
            byte[] bytes = cipher.doFinal(content.getBytes());
//            return Base64.getEncoder().encodeToString(bytes);  //方法加注解：@RequiresApi(api = Build.VERSION_CODES.O)
            return new BASE64Encoder().encode(bytes);
        } catch (IOException | ClassNotFoundException | NoSuchPaddingException | NoSuchAlgorithmException
                | InvalidKeyException | BadPaddingException | IllegalBlockSizeException e) {
            e.printStackTrace();
        }
        return null;
    }

    public static String decrypt(String content) {
        try {
            generateKeypair();
            //取出私钥
            ObjectInputStream privateIs = new ObjectInputStream(new FileInputStream(PRIVATE_KEY_FILE));
            Key privateKey = (Key) privateIs.readObject();
            privateIs.close();

            //开始使用
            Cipher cipher = Cipher.getInstance(ALGORITHM);
            cipher.init(Cipher.DECRYPT_MODE, privateKey);
//            byte[] bytes = Base64.getDecoder().decode(content); //方法加注解：@RequiresApi(api = Build.VERSION_CODES.O)
            byte[] bytes = new BASE64Decoder().decodeBuffer(content);
            return new String(cipher.doFinal(bytes));
        } catch (IOException | ClassNotFoundException | NoSuchPaddingException | InvalidKeyException
                | NoSuchAlgorithmException | IllegalBlockSizeException | BadPaddingException e) {
            e.printStackTrace();
        }
        return null;
    }


    /**********  begin  2019/6/4  TangJian  以下代码还需验证 *********/

    private static final String KEY_ALGORITHM = "RSA"; //加密算法RSA
    private static final String SIGNATURE_ALGORITHM = "MD5withRSA"; //签名算法
    private static final String PUBLIC_KEY = "RSAPublicKey";  //获取公钥的key
    private static final String PRIVATE_KEY = "RSAPrivateKey";  //获取私钥的key
    private static final int MAX_ENCRYPT_BLOCK = 117;  //RSA最大加密明文大小
    private static final int MAX_DECRYPT_BLOCK = 128; //RSA最大解密密文大小

    /**
     * 生成密钥对(公钥和私钥)
     */
    public static Map<String, Object> genKeyPair() throws Exception {
        KeyPairGenerator keyPairGen = KeyPairGenerator.getInstance(KEY_ALGORITHM);
        keyPairGen.initialize(1024);
        KeyPair keyPair = keyPairGen.generateKeyPair();
        RSAPublicKey publicKey = (RSAPublicKey) keyPair.getPublic();
        RSAPrivateKey privateKey = (RSAPrivateKey) keyPair.getPrivate();
        Map<String, Object> keyMap = new HashMap<>(2);
        keyMap.put(PUBLIC_KEY, publicKey);
        keyMap.put(PRIVATE_KEY, privateKey);
        return keyMap;
    }

    /**
     * @param data       已加密数据
     * @param privateKey 私钥(BASE64编码)
     */
    public static String sign(byte[] data, String privateKey) throws Exception {
        byte[] keyBytes = Base64Utils.decode(privateKey);
        PKCS8EncodedKeySpec pkcs8KeySpec = new PKCS8EncodedKeySpec(keyBytes);
        KeyFactory keyFactory = KeyFactory.getInstance(KEY_ALGORITHM);
        PrivateKey privateK = keyFactory.generatePrivate(pkcs8KeySpec);
        Signature signature = Signature.getInstance(SIGNATURE_ALGORITHM);
        signature.initSign(privateK);
        signature.update(data);
        return Base64Utils.encode(signature.sign());
    }

    /**
     * @param data      已加密数据
     * @param publicKey 公钥(BASE64编码)
     * @param sign      数字签名
     */
    public static boolean verify(byte[] data, String publicKey, String sign) throws Exception {
        byte[] keyBytes = Base64Utils.decode(publicKey);
        X509EncodedKeySpec keySpec = new X509EncodedKeySpec(keyBytes);
        KeyFactory keyFactory = KeyFactory.getInstance(KEY_ALGORITHM);
        PublicKey publicK = keyFactory.generatePublic(keySpec);
        Signature signature = Signature.getInstance(SIGNATURE_ALGORITHM);
        signature.initVerify(publicK);
        signature.update(data);
        return signature.verify(Base64Utils.decode(sign));
    }

    /**
     * @param encryptedData 已加密数据
     * @param privateKey    私钥(BASE64编码)
     */
    public static byte[] decryptByPrivateKey(byte[] encryptedData, String privateKey) throws Exception {
        byte[] keyBytes = Base64Utils.decode(privateKey);
        PKCS8EncodedKeySpec pkcs8KeySpec = new PKCS8EncodedKeySpec(keyBytes);
        KeyFactory keyFactory = KeyFactory.getInstance(KEY_ALGORITHM);
        Key privateK = keyFactory.generatePrivate(pkcs8KeySpec);
        Cipher cipher = Cipher.getInstance(keyFactory.getAlgorithm());
        cipher.init(Cipher.DECRYPT_MODE, privateK);
        int inputLen = encryptedData.length;
        ByteArrayOutputStream out = new ByteArrayOutputStream();
        int offSet = 0;
        byte[] cache;
        int i = 0;
        // 对数据分段解密
        while (inputLen - offSet > 0) {
            if (inputLen - offSet > MAX_DECRYPT_BLOCK) {
                cache = cipher.doFinal(encryptedData, offSet, MAX_DECRYPT_BLOCK);
            } else {
                cache = cipher.doFinal(encryptedData, offSet, inputLen - offSet);
            }
            out.write(cache, 0, cache.length);
            i++;
            offSet = i * MAX_DECRYPT_BLOCK;
        }
        byte[] decryptedData = out.toByteArray();
        out.close();
        return decryptedData;
    }

    /**
     * @param encryptedData 已加密数据
     * @param publicKey     公钥(BASE64编码)
     */
    public static byte[] decryptByPublicKey(byte[] encryptedData, String publicKey) throws Exception {
        byte[] keyBytes = Base64Utils.decode(publicKey);
        X509EncodedKeySpec x509KeySpec = new X509EncodedKeySpec(keyBytes);
        KeyFactory keyFactory = KeyFactory.getInstance(KEY_ALGORITHM);
        Key publicK = keyFactory.generatePublic(x509KeySpec);
        Cipher cipher = Cipher.getInstance(keyFactory.getAlgorithm());
        cipher.init(Cipher.DECRYPT_MODE, publicK);
        int inputLen = encryptedData.length;
        ByteArrayOutputStream out = new ByteArrayOutputStream();
        int offSet = 0;
        byte[] cache;
        int i = 0;
        // 对数据分段解密
        while (inputLen - offSet > 0) {
            if (inputLen - offSet > MAX_DECRYPT_BLOCK) {
                cache = cipher.doFinal(encryptedData, offSet, MAX_DECRYPT_BLOCK);
            } else {
                cache = cipher.doFinal(encryptedData, offSet, inputLen - offSet);
            }
            out.write(cache, 0, cache.length);
            i++;
            offSet = i * MAX_DECRYPT_BLOCK;
        }
        byte[] decryptedData = out.toByteArray();
        out.close();
        return decryptedData;
    }

    /**
     * @param data      源数据
     * @param publicKey 公钥(BASE64编码)
     */
    public static byte[] encryptByPublicKey(byte[] data, String publicKey) throws Exception {
        byte[] keyBytes = Base64Utils.decode(publicKey);
        X509EncodedKeySpec x509KeySpec = new X509EncodedKeySpec(keyBytes);
        KeyFactory keyFactory = KeyFactory.getInstance(KEY_ALGORITHM);
        Key publicK = keyFactory.generatePublic(x509KeySpec);
        // 对数据加密
        Cipher cipher = Cipher.getInstance(keyFactory.getAlgorithm());
        cipher.init(Cipher.ENCRYPT_MODE, publicK);
        int inputLen = data.length;
        ByteArrayOutputStream out = new ByteArrayOutputStream();
        int offSet = 0;
        byte[] cache;
        int i = 0;
        // 对数据分段加密
        while (inputLen - offSet > 0) {
            if (inputLen - offSet > MAX_ENCRYPT_BLOCK) {
                cache = cipher.doFinal(data, offSet, MAX_ENCRYPT_BLOCK);
            } else {
                cache = cipher.doFinal(data, offSet, inputLen - offSet);
            }
            out.write(cache, 0, cache.length);
            i++;
            offSet = i * MAX_ENCRYPT_BLOCK;
        }
        byte[] encryptedData = out.toByteArray();
        out.close();
        return encryptedData;
    }

    /**
     * @param data       源数据
     * @param privateKey 私钥(BASE64编码)
     */
    public static byte[] encryptByPrivateKey(byte[] data, String privateKey) throws Exception {
        byte[] keyBytes = Base64Utils.decode(privateKey);
        PKCS8EncodedKeySpec pkcs8KeySpec = new PKCS8EncodedKeySpec(keyBytes);
        KeyFactory keyFactory = KeyFactory.getInstance(KEY_ALGORITHM);
        Key privateK = keyFactory.generatePrivate(pkcs8KeySpec);
        Cipher cipher = Cipher.getInstance(keyFactory.getAlgorithm());
        cipher.init(Cipher.ENCRYPT_MODE, privateK);
        int inputLen = data.length;
        ByteArrayOutputStream out = new ByteArrayOutputStream();
        int offSet = 0;
        byte[] cache;
        int i = 0;
        // 对数据分段加密
        while (inputLen - offSet > 0) {
            if (inputLen - offSet > MAX_ENCRYPT_BLOCK) {
                cache = cipher.doFinal(data, offSet, MAX_ENCRYPT_BLOCK);
            } else {
                cache = cipher.doFinal(data, offSet, inputLen - offSet);
            }
            out.write(cache, 0, cache.length);
            i++;
            offSet = i * MAX_ENCRYPT_BLOCK;
        }
        byte[] encryptedData = out.toByteArray();
        out.close();
        return encryptedData;
    }

    /**
     * 获取私钥
     */
    public static String getPrivateKey(Map<String, Object> keyMap) throws Exception {
        Key key = (Key) keyMap.get(PRIVATE_KEY);
        return Base64Utils.encode(key.getEncoded());
    }

    /**
     * 获取公钥
     */
    public static String getPublicKey(Map<String, Object> keyMap) throws Exception {
        Key key = (Key) keyMap.get(PUBLIC_KEY);
        return Base64Utils.encode(key.getEncoded());
    }
}
